A brazed plate heat exchanger and use thereof

ABSTRACT

A brazed plate heat exchanger ( 100 ) includes a plurality of first and second heat exchanger plates ( 110, 120 ), wherein the first heat exchanger plates ( 110 ) are formed with a first pattern of ridges and grooves, and the second heat exchanger plates ( 120 ) are formed with a second pattern of ridges and grooves providing contact points between at least some crossing ridges and grooves of neighbouring plates under formation of interplate flow channels for fluids to exchange heat, said interplate flow channels being in selective fluid communication through port openings. The first pattern of ridges and grooves is different from the second pattern of ridges and grooves, so that an interplate flow channel volume on one side of the first heat exchanger plates ( 110 ) is different from an interplate flow channel volume on the opposite side of the first heat exchanger plates ( 110 ), and at least some of the ridges and grooves of the first pattern extend in a first angle (β 1 ) and at least some of the ridges and grooves of the second pattern extend in a second angle (β 2 ) different from the first angle (β 1 ).

FIELD OF THE INVENTION

The present invention relates to a brazed plate heat exchanger comprising a plurality of heat exchanger plates having a pattern of ridges and grooves providing contact points between at least some crossing ridges and grooves of neighbouring plates under formation of interplate flow channels for fluids to exchange heat. The present invention is also related to the use of such a heat exchanger.

PRIOR ART

Heat exchangers are used for exchanging heat between fluid media. They generally comprise a start plate, an end plate and a number of heat exchanger plates stacked onto one another in a manner forming flow channels between the heat exchanger plates. Usually, port openings are provided to allow selective fluid flow in and out from the flow channels in a way well known to persons skilled in the art.

A common way of manufacturing a plate heat exchanger is to braze the heat exchanger plates together to form the plate heat exchanger. Brazing a heat exchanger means that a number of heat exchanger plates are provided with a brazing material, after which the heat exchanger plates are stacked onto one another and placed in a furnace having a temperature sufficiently hot to at least partially melt the brazing material. After the temperature of the furnace has been lowered, the brazing material will solidify, whereupon the heat exchanger plates will be joined to one another to form a compact and strong heat exchanger.

It is well known by persons skilled in the art that the flow channels between the heat exchanger plates of a plate heat exchanger are created by providing the heat exchanger plates with a pressed pattern of ridges and grooves. A number of heat exchanger plates are typically stacked on one another, wherein the plates can be identical to provide a symmetric plate heat exchanger or not identical to provide an asymmetric plate heat exchanger. When stacked, the ridges of a first heat exchanger plate contact the grooves of a neighboring heat exchanger plate and the plates are thus kept at a distance from each other through contact points. Hence, flow channels are formed. In these flow channels, fluid media, such as a first and second fluid media are lead so that heat transfer is obtained between such media.

A plurality of brazed plate heat exchangers with a pressed corrugated pattern having ridges and grooves in a herringbone pattern is known in the prior art. However, there is a need to improve such prior art heat exchangers.

It is the object of the present invention to provide a plate heat exchanger with favourable flow distribution, pressure drop and heat transfer between the fluid media.

SUMMARY OF THE INVENTION

According to the invention, the above object is achieved by a brazed plate heat exchanger (BPHE) comprising a plurality of first and second heat exchanger plates, wherein the first heat exchanger plates are formed with a first pattern of ridges and grooves, and the second heat exchanger plates are formed with a second pattern of ridges and grooves providing contact points between at least some crossing ridges and grooves of neighbouring plates under formation of interplate flow channels for fluids to exchange heat, said interplate flow channels being in selective fluid communication through port openings, characterised in that the first pattern of ridges and grooves is different from the second pattern of ridges and grooves, so that an interplate flow channel volume on one side of the first heat exchanger plates is different from an interplate flow channel volume on the opposite side of the first heat exchanger plates, and at least some of the ridges and grooves of the first pattern extend in a first angle and at least some of the ridges and grooves of the second pattern extend in a second angle different from the first angle. The combination of different interplate flow channel volumes on opposite sides of the plates and at least two different plate patterns having different angles result in a BPHE with favourable properties for fluid distribution, wherein the fluid flow distribution and pressure drop can be balanced to achieve efficient heat exchange. This makes it possible to achieve different properties in interplate flow channels on opposite sides of the same plate, wherein the flow and pressure drop on one side can be different from the opposite side. Also, the different flow channel volumes on opposite sides of the plates can be used for different types of medias, such as a liquid in one and a gas in the other.

When a refrigerant start to evaporate it is transferred from a liquid state to a vapour state. The liquid has a density that is much higher than the vapour density. For example R410A at Tdew=5° C. has 32 times higher density for the liquid than the vapour. This also mean that the vapour will move in a channel at velocities that are 32 times higher than the liquid. This will automatically lead to the dynamic pressure drop for the vapour being 32 times higher than for the liquid, i.e. vapour creates much higher pressure drop for all kind of refrigerants.

The performance (Temperature Approach, TA) of a heat exchanger is defined as the water outlet temperature (at the inlet of the heat exchanger channel) minus the evaporation temperature (Tdew) at the outlet of the heat exchanger channel. A high pressure drop along the heat exchanger surface results in different local saturation temperatures that will result in a relatively large total difference in refrigerant temperature between the inlet and outlet of the channel. The temperature will be higher at the inlet of the channel. This will have a direct, detrimental impact on the performance of the heat exchanger, since a higher inlet refrigerant temperature (due to too high channel pressure drop) makes it harder to cool the outlet water to the correct temperature. The only way for the system to compensate for the too high refrigerant inlet temperature is by lowering the evaporation temperature until correct water outlet temperature can be reached. By creating pattern for heat exchanger channels that have high heat transfer characteristics and at the same time have low pressure drop characteristics, a higher performance can be reached for the heat exchanger. A lower overall refrigerant pressure drop in the channel will not only improve the heat exchanger performance it will also have a positive impact on the total system performance and, hence, the energy consumption.

At least one of the first and second heat exchanger plates can be an asymmetric heat exchanger plate. Alternatively, the first heat exchanger plates are formed with another corrugation width than the second heat exchanger plates. The first heat exchanger plate can be a symmetric heat exchanger plate, wherein the second heat exchanger plate can be an asymmetric heat exchanger plate. Hence, first grooves of the second heat exchanger plates can be formed with a first depth, and second grooves of the second heat exchanger plates can be formed with a second depth different from the first depth. Through the combination of different angles and corrugation depth patterns, the fluid flow distribution and pressure drop can be customized for the application to achieve efficient heat exchange. The patterns of ridges and grooves can be herringbone patterns, wherein the angles of the pattern of ridges and grooves are chevron angles.

Furthermore, the depths of the first and second heat exchanger plates may differ from each other in a way that the interplate flow channels have different sizes seen in cross section, wherein the interplate flow channels have different volumes on opposite sides of the plates. Hence, the interplate flow channels can have different cross section areas on opposite sides of the plates. This provides an asymmetric plate heat exchanger that combines favourable heat transfer with low pressure drop to achieve a more efficient heat exchanger for various purposes, such as for heating, refrigeration or a reversible refrigeration system.

The first and second patterns can be herringbone patterns or patterns where the ridges and grooves extend in oblique straight lines over the heat exchanger plate. Hence, the angles are in a plane of the heat exchanger plates, e.g. towards a side of the heat exchanger plates. For example, the angle is between a short side of a rectangular heat exchanger plate and the extension of the ridges and grooves. The first and second angles, such as first and second chevron angles, can be 0-90°, 25-70° or 30-45°. Hence, the angles can be selected to achieve favourable fluid distribution. The difference between the first and second angles can be 2-35°. The first and second patterns can be in opposite directions, wherein the first and second angles are in opposite directions, such as towards opposite short sides of rectangular heat exchanger plates.

Disclosed is also the use of a brazed plate heat exchanger according to the present invention for evaporation or condensation of media.

Further characteristics and advantages of the present invention will become apparent from the description of the embodiments below, the appended drawings and the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described with reference to appended drawings, wherein:

FIG. 1 is a schematic and exploded perspective view of a heat exchanger according to one embodiment of the present invention,

FIG. 2 is an exploded perspective view of a part of the heat exchanger of FIG. 1 , illustrating a first heat exchanger plate and a second heat exchanger plate of the heat exchanger,

FIG. 3 is a schematic section view of a part of the first heat exchanger plate according to one embodiment, illustrating identical depth of grooves of the first heat exchanger plate,

FIG. 4 is a schematic section view of a part of the second heat exchanger plate according to one embodiment, illustrating an alternating depth of grooves of the second heat exchanger plate,

FIG. 5 is a schematic section view of a part of a heat exchanger comprising first and second heat exchanger plates according to one embodiment, wherein the first and second heat exchanger plates are alternatingly arranged,

FIG. 6 a is a schematic front view of the first heat exchanger plate according to one embodiment, illustrating a corrugated herringbone pattern thereof having a first angle in the form of a chevron angle,

FIG. 6 b is a schematic front view of the first heat exchanger plate according to an alternative embodiment, illustrating a corrugated pattern thereof having a first angle,

FIG. 7 a is a schematic front view of the second heat exchanger plate according to one embodiment, illustrating a corrugated herringbone pattern thereof having a second angle in the form of a chevron angle,

FIG. 7 b is a schematic front view of the second heat exchanger plate according to an alternative embodiment, illustrating a corrugated pattern thereof having a second angle,

FIG. 8 is a schematic view of the first heat exchanger plate arranged on the second heat exchanger plate, illustrating contact points between them according to the example of FIG. 5 ,

FIG. 9 is a schematic view of the second heat exchanger plate arranged on the first heat exchanger plate, illustrating contact points between them according to the example of FIG. 5 ,

FIG. 10 is a schematic cross section view of a part of a heat exchanger comprising first and second heat exchanger plates according to another embodiment,

FIG. 11 is a schematic cross section view of a part of a heat exchanger comprising first and second heat exchanger plates according to another embodiment,

FIG. 12 is a schematic cross section view of a part of a heat exchanger comprising first and second heat exchanger plates according to yet another embodiment,

FIG. 13 is a schematic cross section view of a part of a stack of heat exchanger plates of first and second heat exchanger plates having different corrugation depths according to another embodiment, and

FIG. 14 is a schematic perspective view of a plate heat exchanger illustrating another embodiment of the corrugated pattern, wherein the angle of the corrugated pattern in a central main heat exchanging section differs from the angle in sections at port openings of the heat exchanger plates.

DESCRIPTION OF EMBODIMENTS

With reference to FIG. 1 a brazed plate heat exchanger 100 is illustrated according to one embodiment, wherein a part thereof is illustrated more in detail in FIG. 2 . The heat exchanger 100 comprises a plurality of first heat exchanger plates 110 and a plurality of second heat exchanger plates 120 stacked in a stack to form the heat exchanger 100. The first and second heat exchanger plates 110, 120 are arranged alternatingly, wherein every other plate is a first heat exchanger plate 110 and every other plate is a second heat exchanger plate 120. Alternatively, the first and second heat exchanger plates are arranged in another configuration together with additional heat exchanger plates. The heat exchanger 100 is an asymmetric plate heat exchanger.

The heat exchanger plates 110, 120 are made from sheet metal and are provided with a pressed pattern of ridges R1, R2 a, R2 b and grooves G1, G2 a, G2 b such that interplate flow channels for fluids to exchange heat are formed between the plates when the plates are stacked in a stack to form the heat exchanger 100 by providing contact points between at least some crossing ridges and grooves of neighbouring plates 110, 120 under formation of the interplate flow channels for fluids to exchange heat. The pressed pattern of FIGS. 1 and 2 is a herringbone pattern. However, the pressed pattern may also be in the form of obliquely extending straight lines. In any case, the pressed pattern of ridges and grooves is a corrugated pattern. The pressed pattern is adapted to keep the plates 110, 120 on a distance from one another, except from the contact points, to form the interplate flow channels.

In the illustrated embodiment, each of the heat exchanger plates 110, 120 is surrounded by a skirt S, which extends generally perpendicular to a plane of the heat exchanger plate and is adapted to contact skirts of neighbouring plates in order to provide a seal along the circumference of the heat exchanger. Apart from the skirt S and ports O1-O4 practically the remaining part of the heat exchanger plates 110, 120 forms a heat exchanging surface 130, 140.

The heat exchanger plates 110, 120 are arranged with port openings O1-O4 for letting fluids to exchange heat into and out of the interplate flow channels. In the illustrated embodiment, the heat exchanger plates 110, 120 are arranged with a first port opening O1, a second port opening O2, a third port opening O3 and a fourth port opening O4. Areas surrounding the port openings O1 to O4 are provided at different heights such that selective communication between the port openings and the interplate flow channels is achieved. In the heat exchanger 100, the areas surrounding the port openings O1-O4 are arranged such that the first and second port openings O1 and O2 are in fluid communication with one another through some interplate flow channels, whereas the third and fourth port openings O3 and O4 are in fluid communication with one another by neighboring interplate flow channels. In the illustrated embodiment, the heat exchanger plates 110, 120 are rectangular with rounded corners, wherein the port openings O1-O4 are arranged near the corners. Alternatively, the heat exchanger plates 110, 120 are square, e.g. with rounded corners. Alternatively, the heat exchanger plates 110, 120 are circular, oval or arranged with other suitable shape, wherein the port openings O1-O4 are distributed in a suitable manner. In the illustrated embodiment, each of the heat exchanger plates 110, 120 is formed with four port openings O1-O4.

Please note that in other embodiments of the invention, the number of port openings may be larger than four, i.e. six, eight or ten. For example, the number of port openings is at least six, wherein the heat exchanger is configured for providing heat exchange between at least three fluids. Hence, according to one embodiment, the heat exchanger is a three circuit heat exchanger having at least six port openings and in addition being arranged with or without at least one integrated suction gas heat exchanger. Alternatively, the number of port openings is at least six, wherein the heat exchanger includes one or more integrated suction gas heat exchangers.

In the illustrated embodiment, the heat exchanger 100 comprises only the first and second heat exchanger plates 110, 120. Alternatively, the heat exchanger 100 comprises a third and optionally also a fourth heat exchanger plate, wherein the third and optional fourth heat exchanger plates are arranged with different pressed patterns than the first and second heat exchanger plates 110, 120, and wherein the heat exchanger plates are arranged in a suitable order.

In the illustrated embodiment, the heat exchanger 100 also comprises a start plate 150 and an end plate 160. The start plate 150 is formed with openings corresponding to the port openings O1-O4 for letting fluids into and out of the interplate flow channels formed by the first and second heat exchanger plates 110, 120. For example, the end plate 160 is a conventional end plate.

With reference to FIG. 3 , a section view of the first heat exchanger plate 110 according to one embodiment is illustrated schematically. The first heat exchanger plates 110 are formed with a first pattern of ridges R1 and grooves G1. The grooves G1 of the first heat exchanger plates are formed with identical depth D1. Hence, all grooves G1 are formed with the same depth D1. For example, the depth D1 is 0.5-5 mm, such as 1-3 mm or 1.5-3 mm. For example, all ridges R1 are formed with the same height in a corresponding manner. In other words, the corrugation depth of the first heat exchanger plates 110 is symmetrical and similar throughout the plate or at least substantially throughout the plate.

With reference to FIG. 4 , a section view of the second heat exchanger plate 120 is illustrated schematically according to one embodiment. For example, all second heat exchanger plates 120 are identical. The second heat exchanger plates 120 are formed with a second pattern of first and second ridges R2 a, R2 b and first and second grooves G2 a, G2 b. The first and second grooves G2 a, G2 b of the second heat exchanger plates 120 are formed with different depths, wherein the first grooves G2 a are formed with a first depth D2 a, and the second grooves G2 b are formed with a second depth D2 b, wherein the second depth D2 b is different from the first depth D2 a. For example, the first depth D2 a is 0.5-5 mm, such as 0.5-3 mm, wherein the second depth D2 b is 30-80% of the first depth D2 a, such as 40-60% thereof. The ridges R2 a, R2 b have different heights in a corresponding manner. In the illustrated embodiment, the first depth D2 a is larger than the second depth D2 b. The first and second grooves G2 a, G2 b are arranged alternatingly. Alternatively, the first and second grooves G2 a, G2 b, and optionally further grooves having other depths, are arranged in any desired pattern. For example, the pattern of ridges and grooves of the second heat exchanger plates 120 is asymmetrical, i.e. the second heat exchanger plates 120 would form an asymmetric heat exchanger when combined with first heat exchanger plates 110 such as shown below with reference to FIG. 5 . According to one embodiment, the entire heat exchanging surface of the second heat exchanger plates 120 is formed with the second pattern of ridges and grooves having at least two different corrugation depths D2 a, D2 b of the grooves.

With reference to FIG. 5 a plurality of the first and second heat exchanger plates 110, 120 have been stacked to schematically illustrate formation of interplate flow channels according to one embodiment. In the illustrated embodiment, every other plate is a first heat exchanger plate 110 and the remaining plates are second heat exchanger plates 120, wherein the first and second heat exchanger plates are arranged alternatingly to form an asymmetric heat exchanger 100, wherein the interplate flow channels are formed with different volumes. Alternatively, the different volumes of the interplate flow channels are formed by an extended profile on the same press depth or corrugation depth. For example, the first and second heat exchanger plates are provided with different corrugation depths. For example, the first and/or second heat exchanger plates is/are asymmetric heat exchanger plates. Alternatively, the first and/or second heat exchanger plates is/are symmetric heat exchanger plates.

With reference to FIG. 6 a the first pattern of ridges R1 and grooves G1 of the first heat exchanger plate 110 is illustrated schematically. Said pattern is a pressed herringbone pattern, wherein the ridges R1 and grooves G1 are arranged with two inclined legs meeting in an apex, such as a centrally arranged apex, forming an arrow pattern. For example, said legs of the ridges R1 and grooves G1 are equally long. For example, the apices are distributed along an imaginary centre line, such as a longitudinal centre line of a rectangular heat exchanger plate. For example, the herringbone pattern is arranged so that ridges R and grooves G extend from one long side to the other of the first heat exchanger plate 110, e.g. with all the apices pointing towards one of the short sides. The pattern of the first heat exchanger plate 110, i.e. the first pattern of ridges R1 and grooves G1, exhibits a first chevron angle β1. The chevron angle is the angle between the ridge and an imaginary line across the plate, perpendicular to the long sides of a rectangular plate, which is illustrated schematically by means of the dashed line C. Hence, the chevron angle is the angle between the leg of the ridge and a short side of the heat exchanger plate towards which the apex is pointing. The long sides of the heat exchanger plates extend perpendicular to the short sides and hence the pattern of ridges and grooves is also arranged so that the ridges have an angle to the long sides. For example, the chevron angle is the same on both sides of the apex. For example, the entire or substantially entire first pattern of ridges and grooves is formed with the first chevron angle β1 throughout the heat exchanging surface 130 of the plate. For example, the first chevron angle β1 is between 5° and 85°, 25° and 70° or 40° and 65°.

With reference to FIG. 6 b the first pattern of ridges R1 and grooves G1 of the first heat exchanger plate 110 is illustrated schematically according to an alternative embodiment, wherein the pressed pattern is in the form of obliquely extending straight lines. Hence, the pressed pattern of ridges and grooves is a corrugated pattern of obliquely extending straight lines. The obliquely extending straight lines of the first heat exchanger plates 110 are arranged in the angle β1. For example, the pattern is arranged so that ridges R1 and grooves G1 extend, e.g. in parallel, from one long side to the other of the first heat exchanger plate 110.

With reference to FIG. 7 a the second pattern of ridges R2 a, R2 b and grooves G2 a, G2 b of the second heat exchanger plate 120 is illustrated schematically. Said second pattern is a pressed herringbone pattern as described above with reference to the first heat exchanger plate 110 but with a second chevron angle β2 different from the first chevron angle β1. Hence, the second heat exchanger plate 120 is arranged with a herringbone pattern having a different angle than the first heat exchanger plate. For example, the second chevron angle β2 is between 5° and 85°, 25° and 70° or 40° and 65°. For example, the entire or substantially entire pattern of ridges and grooves of the second heat exchanger plates 120 is formed with the second chevron angle β2 throughout the heat exchanging surface 140 of the plate. The second pattern of ridges R2 a, R2 b and grooves G2 a, G2 b is arranged in the opposite direction as the first pattern of ridges R1 and grooves G1. The apices of the herringbone pattern of the second heat exchanger plate 120 point in the opposite direction as the apices of the herringbone pattern of the first heat exchanger plate 110. Hence, the apices of the first pattern of ridges R1 and grooves G1 point toward one short side of the first heat exchanger plate 110, wherein the apices of the second pattern of ridges R2 a, R2 b and grooves G2 a, G2 b point toward the opposite short side of the second heat exchanger plate 120, so that the herringbone patterns alternatingly are arranged in opposite directions throughout the heat exchanger 100. Hence, the first and second angles β1, β2 are in opposite directions. For example, the first angle β1 is towards one short side of the heat exchanger plates and the second angle β2 is towards the opposite short side.

With reference to FIG. 7 b the second pattern of ridges R2 a, R2 b and grooves G2 a, G2 b of the second heat exchanger plate 120 is illustrated schematically according to an alternative embodiment, wherein the pressed pattern is in the form of obliquely extending straight lines. Hence, the pressed pattern of ridges and grooves is a corrugated pattern of obliquely extending straight lines. The obliquely extending straight lines of the second heat exchanger plates 120 are arranged in the angle β2. For example, the pattern is arranged so that ridges R and grooves G extend, e.g. in parallel, from one long side to the other of the second heat exchanger plate 120. The second pattern of ridges R2 a, R2 b and grooves G2 a, G2 b is arranged in the opposite direction as the first pattern of ridges R1 and grooves G1. The pattern of the second heat exchanger plate 120 is oblique in the opposite direction as the pattern of obliquely extending straight lines of the first heat exchanger plate 110, so that the patterns alternatingly are arranged in opposite directions throughout the heat exchanger 100. For example, the first angle β1 is towards one short side of the heat exchanger plates and the second angle β2 is towards the opposite short side.

Hence, the first and second heat exchanger plates 110, 120 are formed with different chevron angles β1, β2 and different pressed patterns resulting in different interplate volumes. For example, the first and second heat exchanger plates 110, 120 are provided with different corrugation depths. Alternatively or in addition, the first and second heat exchanger plates 110, 120 are provided with different corrugation frequencies. For example, the first and second heat exchanger plates 110, 120 are provided with the same corrugation depth but different corrugation frequencies. Hence, the first and second heat exchanger plates 110, 120 are provided with different corrugation depths and/or different corrugation frequencies. For example, one of the first and second heat exchanger plates 110, 120 is a symmetric heat exchanger plate, wherein the other is asymmetric. Alternatively, both the first and second heat exchanger plates 110, 120 are asymmetric. Alternatively, both the first and second heat exchanger plates 110, 120 are symmetric.

In FIGS. 8 and 9 contact points between the first and second plates 110, 120 are illustrated schematically using the example of FIG. 5 . In and/or around the contact points 170 between crossing ridges and grooves brazing joints 170 are formed. In the embodiment of FIGS. 8 and 9 brazing joints 170 are formed in all contact points. Alternatively, brazing joints 170 are formed in only some of the contact points. In FIG. 8 the first heat exchanger plate 110 is arranged on the second heat exchanger plate 120, wherein contact points are formed in a first pattern. In FIG. 8 all crossings between the ridges R1 of the first heat exchanger plate 110 and ridges or grooves of the second heat exchanger plate 120 result in a contact point.

FIG. 9 is a schematic view of the second heat exchanger plate 120 arranged on the first heat exchanger plate 110, wherein contact points are formed in a second pattern. In FIG. 9 only crossings between the first ridges R2 a of the second heat exchanger plate 120 result in a contact point, which may form a brazing joint 170, wherein the second ridges R2 b are arranged with a gap to the crossing ridges or grooves of the first heat exchanger plate 110. Hence, and no contact points are formed, and no brazing joint is formed, between the second ridges R2 b of the second heat exchanger plate 120 and the first heat exchanger plate 110. In FIG. 9 all contact points are showed with a brazing joint 170.

According to one embodiment, the brazing joints 170 between the first and second heat exchanger plates 110, 120 are elongated, such as oval, wherein the brazing joints 170 are arranged in a first orientation in the interplate flow channels having bigger volume and in a second orientation in the interplate flow channels having smaller volume to provide a favourable pressure drop in the desired interplate flow channels. For example, the brazing joints 170 are arranged in a first angle in relation to a longitudinal direction of the plates 110, 120 in the interplate flow channels having bigger volume and in a second angle in the remaining interplate flow channels. According to one embodiment, the first angle is bigger than the second angle.

With reference to FIG. 10 a cross section of a part of a heat exchanger comprising first and second heat exchanger plates 110, 120 according to another embodiment is illustrated schematically. In the embodiment of FIG. 10 the first heat exchanger plate 110 is a symmetric heat exchanger plate, wherein the second heat exchanger plate 120 is an asymmetric heat exchanger plate as described above. Hence, the corrugation depth of the first heat exchanger plate 110 is constant, wherein the corrugation depth of the second heat exchanger plate 120 is varying. The second heat exchanger plate 120 is formed with at least two different corrugation depths. Also, the first and second heat exchanger plates 110, 120 are formed with corrugated patterns different angles, such as chevron angles, as described above. In the embodiment of FIG. 10 the chevron angle of the first heat exchanger plate 110 is 54 degrees, wherein the chevron angle of the second heat exchanger plate 120 is 61 degrees. For example, neighbouring interplate volumes are different, so that the interplate volume on one side of the first heat exchanger plates 110 is different from the interplate volume on the opposite side of the first heat exchanger plates 110. Of course, this also apply for the second heat exchanger plates 120. Hence, the interplate volume between the first and second heat exchanger plates is different from the interplate volume between the second and first heat exchanger plates. Similarly, a cross section area on one side of the first heat exchanger plates 110 is different from the cross section area on the opposite side of the first heat exchanger plates 110.

With reference to FIG. 11 a cross section of a part of a heat exchanger comprising first and second heat exchanger plates 110, 120 according to yet another embodiment is illustrated schematically. In the embodiment of FIG. 11 the first heat exchanger plate 110 is a symmetric heat exchanger plate, wherein the second heat exchanger plate 120 is an asymmetric heat exchanger plate as described above. In the embodiment of FIG. 11 the chevron angle of the first heat exchanger plate 110 is 45 degrees, wherein the chevron angle of the second heat exchanger plate 120 is 61 degrees.

With reference to FIG. 12 a cross section of a part of a heat exchanger comprising first and second heat exchanger plates 110, 120 according to yet another embodiment is illustrated schematically. In the embodiment of FIG. 12 the first heat exchanger plate 110 is an asymmetric heat exchanger plate, wherein the second heat exchanger plate 120 is also an asymmetric heat exchanger plate. In the embodiment of FIG. 12 the chevron angle of the first heat exchanger plate 110 is different from the chevron angle of the second heat exchanger plate 120 as described above. Also, the interplate flow channels have different volumes as described above. For example, the brazing joints are elongated, such as oval, and arranged in a first orientation in the interplate flow channels having bigger volume and in a different, second orientation in the interplate flow channels having smaller volume.

With reference to FIG. 13 a cross section of a part of a stack of first and second heat exchanger plates 110, 120 according to yet another embodiment is illustrated schematically. In the embodiment of FIG. 13 the first and second heat exchanger plates 110, 120 are provided with different corrugation depths. The first heat exchanger plate 110 is a symmetric heat exchanger plate, wherein the second heat exchanger plate 120 is an asymmetric heat exchanger plate. Alternatively, both the first and second heat exchanger plates 110, 120 are symmetric or asymmetric. The chevron angle of the first heat exchanger plate 110 is different from the chevron angle of the second heat exchanger plate 120 and the interplate flow channel volumes formed by the first and second heat exchanger plates 110, 120 when brazed together in brazing joints are different.

The heat exchanger according to the present invention is, e.g. used for condensation or evaporation, wherein at least one media at some point is in gaseous phase. For example, the heat exchanger is used for heat exchange, wherein condensation or evaporation takes place in the interplate flow channels of bigger volume. For example, a liquid media, such as water or brine, is conducted through the interplate flow channels having smaller volume.

With reference to FIG. 14 the first pattern of ridges R1 and grooves G1 of the first heat exchanger plate 110 is illustrated schematically. The pressed pattern according to the embodiment of FIG. 14 is a herringbone pattern but may alternatively be a pattern of oblique lines and thus exhibits the first angle β1 generally as described above with reference to FIGS. 6 a and 6 b . However, in the embodiment of FIG. 14 the first angle β1 is in a central main heat exchanging section of the heat exchanger plate 110. Hence, the first pressed pattern partially comprises the first angle β1. For example, the central main heat exchanging section extends across the first heat exchanger plate 110 from one side to the opposite side. The central main heat exchanging section is arranged between first and second heat exchanging sections at port openings of the heat exchanger plate, called end sections herein. The first and second end sections are, for example, arranged at opposite ends of the first heat exchanger plate 110. For example, the first and second end sections extend across the first heat exchanger plate 110 from one side to the opposite side thereof and optionally also extends to a third side, such as a short side, of the heat exchanger plates. The first end section includes port openings, such as the first port opening O1 and the third port opening O3. The second end section includes port openings, such as the second and fourth port openings O2, O4. The pressed pattern of ridges and grooves R1, G1 is arranged with an angle β1′ in at least one end section, such as the first and/or second end sections, which angle β1′ differs from the angle β1 of the pressed pattern in the central main heat exchanging section. For example, the direction of the pressed pattern is the same in the central main section as in the end sections. For example, the angle is the same in both end sections. Alternatively, the angle in the first end section is different from the angle in the second end section. Optionally, the second heat exchanging portion 140 is arranged with a pattern or an angle different from the first end section. Hence, at least some of the ridges and grooves of the first heat exchanger plate 110 extend in the first angle β1, wherein others extend in the different angle β1′. Hence, the first pattern is at least partially arranged with the first angle β1. For example, the first angle β1 is bigger than the different angle β1′.

In FIG. 14 the first heat exchanger plate 110 is illustrated as an example but it is understood that the second pressed pattern of the second heat exchanger plate 120 is designed in a corresponding manner, wherein the second pattern of ridges R2 a, R2 b and grooves G2 a, G2 b is arranged with the angle β2 in the central main heat exchanging section and one or more of the end sections are arranged with a different angle β2′ (not illustrated). Hence, also for the second heat exchanger plates 120, at least some of the ridges R2 a, R2 b and grooves G2 a, G2 b extend in the angle β2, wherein others extend in the differing angle β2′. Hence, the second pattern is at least partially arranged with the second angle β2. The second angle β2 is, e.g. in the opposite direction as the first angle β1. Hence, in the embodiment of herringbone patterns, the first pattern exhibit chevrons in the opposite direction as chevrons of the second pattern and hence chevron angles in opposite directions.

In FIG. 14 the first heat exchanger plate 110 comprises small port openings SO1, SO2 and a dividing surface DW to provide a separate heat exchanging section which can form an integrated suction gas heat exchanger of a heat exchanger comprising alternatingly arranged first and second plates 110, 120 with such a design. 

1. A brazed plate heat exchanger comprising a plurality of first and second heat exchanger plates, wherein the first heat exchanger plates are formed with a first pattern of ridges and grooves, and the second heat exchanger plates are formed with a second pattern of ridges and grooves providing contact points between at least some crossing ridges and grooves of neighbouring plates under formation of interplate flow channels for fluids to exchange heat, said interplate flow channels being in selective fluid communication through port openings, wherein the first pattern of ridges and grooves is different from the second pattern of ridges and grooves, so that an interplate flow channel volume on one side of the first heat exchanger plates is different from the interplate flow channel volume on the opposite side of the first heat exchanger plates, and at least some of the ridges and grooves of the first pattern extend in a first angle and at least some of the ridges and grooves of the second pattern extend in a second angle different from the first angle.
 2. The brazed plate heat exchanger of claim 1, wherein the interplate flow channels on one side of the first heat exchanger plates have a different cross section area than on the opposite side.
 3. The brazed plate heat exchanger of claim 1, wherein at least a central main heat exchanging section of the first heat exchanger plates exhibits the first angle, wherein at least a central main heat exchanging section of the second heat exchanger plates exhibits the second angle.
 4. The brazed plate heat exchanger of claim 1, wherein the first heat exchanger plates are symmetric.
 5. The brazed plate heat exchanger of claim 1, wherein the grooves of the first heat exchanger plates are formed with identical corrugation depth, wherein first grooves of the second heat exchanger plates are formed with a first depth, and second grooves of the second heat exchanger plates are formed with a second depth different from the first depth.
 6. The brazed plate heat exchanger of claim 1, wherein a depth of the grooves of the first heat exchanger plate is in the range of 0.6-2 mm.
 7. The brazed plate heat exchanger of claim 1, wherein a first depth of the second heat exchanger plate is in the range of 0.6-3 mm, and a second depth of the second heat exchanger plate is in the range of 30-80% of the first depth.
 8. The brazed plate heat exchanger of claim 1, wherein the first angle of the first pattern of ridges and grooves is in the range of 25-70°.
 9. The brazed plate heat exchanger of claim 1, wherein the second angle of the second pattern of ridges and grooves is in the range of 25-70°.
 10. The brazed plate heat exchanger of claim 1, wherein a difference between the first angle of the first pattern of ridges and grooves and the second angle of the second pattern of ridges and grooves is in the range of 2-35°.
 11. The brazed plate heat exchanger of claim 1, wherein the first and second heat exchanger plates are provided with different corrugation depths.
 12. The brazed plate heat exchanger of claim 1, wherein the heat exchanger plates are provided with different corrugation widths.
 13. The brazed plate heat exchanger of claim 1, wherein the first pattern is a first herringbone pattern or a first pattern of obliquely extending straight lines and the second pattern is a second herringbone pattern or a second pattern of obliquely extending straight lines, and wherein ridges and grooves of the first and second patterns extend from one long side of the heat exchanger plates to the other, and wherein the first angle is towards one short side of the heat exchanger plates and the second angle is towards the opposite short side.
 14. The brazed plate heat exchanger of claim 1, wherein the first and second heat exchanger plates are arranged alternatingly, wherein every other plate is a first heat exchanger plate and every other plate is a second heat exchanger plate throughout the heat exchanger.
 15. The brazed plate heat exchanger of claim 1, wherein brazing points between the first and second heat exchanger plates are elongated and arranged in a first orientation in the interplate flow channels having bigger volume and in a second orientation in the interplate flow channels having smaller volume.
 16. A method for exchanging heat by a brazed heat exchanger according to claim 1, wherein media is evaporated or condensed in the interplate flow channels of smaller volume, wherein liquid media is conducted to the interplate flow channels of bigger volume.
 17. (canceled) 